Location from My Hero Academia by Kohei Horikoshi
Japan's maximum-security villain prison, an isolated ocean fortress designed to contain the most dangerous criminals in the world. Held All For One, Stain, Muscular, and other S-class threats until the catastrophic prison break shattered its walls and released them all.
Tartarus was supposed to be inescapable. Built on the assumption that society would always have heroes strong enough to put villains away and keep them there. When All For One orchestrated the prison break from inside his cell — simultaneously triggering breaks at six other prisons — the facility's security collapsed in minutes. The mass breakout flooded Japan with its worst nightmares and proved that the hero system's approach to villainy was containment, never resolution.
A brutalist concrete and steel fortress rising from an artificial island far offshore. Multiple security rings surround the core facility — automated gun turrets, surveillance drones, reinforced sea walls. The interior is sterile white corridors and heavy vault doors leading to individually designed containment cells. All For One's cell was the deepest, sealed behind multiple biometric locks.
Also known as: Tartarus, Tartarus Prison